In the never-ending war on weight, and since the back seat is mostly for looks, and the arm pads vestigial ...
A sheet of acrylic from the local home destruction store, cut to fit and topped with some plastidip rubber. Some silicon to keep them in place once they're dry. If they don't work out, they will be relatively easy to replace with the pads.
test fit
Those look clean. :)
So...3Lbs saved maybe? Those do look pretty decent though.
Yeah, that's about right. It's cheap weight and easy to do. A MM K is about $30/lb saved, this is about $2/lb saved.